Robotic end effector with counter-rotating fingers

ABSTRACT

A method of handling an object using a robot end effector. The method includes providing a robot having an end effector supporting a pair of carriages, providing a pair of fingers for each carriage, moving the end effector over an object, grasping an object with the fingers, moving the object with the end effector to a container, and depositing the object by counter-rotating the pairs of fingers. One or both of the carriages is movable toward the other carriage to engage objects on a conveyor system with the fingers. The robot moves the end effector between the conveyor system and shipping containers for shipping the objects. Because the pairs of fingers counter-rotate, the friction forces between each finger and the tray is offset by the friction forces between the other finger in the pair and the tray. The improved handling method thereby maintains objects substantially in the desired stacking orientation within the shipping container. Preferably, an actuator is provided for each finger. A change-out mechanism may also be provided to facilitate replacing the fingers.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/521,226, filed Mar. 8, 2000, now U.S. Pat. No. 6,474,047, whichclaims the benefit of U.S. Provisional Application No. 60/124,427, filedon Mar. 15, 1999.

FIELD OF THE INVENTION

The present invention relates to systems and devices used to loadcontainers. More particularly, the present invention relates to arobotic end effector used to load mail trays of different shapes andsizes into containers.

BACKGROUND OF THE INVENTION

Millions of pieces of mail are deposited with the postal service everyday. The deposited mail is sorted, generally by ZIP or other code, andshipped to the proper destination. Generally, the sorting processinvolves placing mail with the same or related codes into trays. Thetrays are then placed in containers for shipment. Some parts of thisprocess have been automated, including the sorting of mail by ZIP code.However, the trays are often placed in the containers manually. Withever-increasing mail demands, faster, more efficient methods of anddevices for loading containers with mail trays are needed.

SUMMARY OF THE INVENTION

The present invention provides an improved end effector for handlingmail trays and tubs. The end effector includes first and secondcarriages, each having a pair of fingers depending therefrom. At leastone of the carriages is movable toward the other carriage to grasp atray between the respective pairs of fingers. The pairs of fingerscounter-rotate to cause the support portions to engage and disengage thetray.

Each carriage has a body and first and second fingers. Each finger has asupport portion and a journal portion having a longitudinal axis. Thejournal portion of each finger is supported by the body for rotationabout the longitudinal axis. The support portion is angled with respectto the longitudinal axis. At least one actuator selectively causes thejournal portions to counter-rotate with respect to each other. Becausethe fingers counter-rotate with respect to each other, the frictionforces between each finger and the tray offset the friction forcesbetween the other finger and the tray, such that the tray remainssubstantially in the desired stacking orientation.

In a preferred construction, the carriage includes first and secondactuators, and the first and second actuators cause the first and secondfingers, respectively, to selectively rotate. A pair of spaced-apartjournal bearings supports the journal portion of each finger forrotation with respect to the body. A split clamp and actuator arm may bedisposed between each pair of journal bearings to interconnect eachfinger with an associated actuator. The clamp includes a change-outmechanism to facilitate replacement of the fingers. Spacers may beprovided to facilitate rotation of the fingers, clamps, and actuatorarms with respect to the body.

Preferably, the end effector also includes a harness assembly for supplylines between the end effector and the rest of the robot. The harnessreduces the likelihood of tangling and pinching the supply lines as theend effector moves with respect to the rest of the robot. The endeffector also preferably includes a shelf lowering mechanism tomanipulate shelves in the containers.

The present invention also provides a method for handling a tray. Themethod includes using an end effector having fingers to pick up and movethe tray to a container, and counter-rotating the fingers to release thetray in the container.

Other features and advantages of the invention will become apparent tothose skilled in the art upon review of the following detaileddescription, claims, and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially exploded, perspective view of a system embodyingthe present invention.

FIG. 2 is an enlarged perspective view of an end effector from thesystem in FIG. 1 taken from above the end effector.

FIG. 3 is a perspective view of the end effector of FIG. 2 taken frombelow the end effector.

FIG. 4 is a side elevational view of the end effector of FIG. 2.

FIG. 5 is an end view of the end effector of FIG. 2.

FIG. 6A is an enlarged exploded view of a carriage of the end effectorof FIG. 2.

FIG. 6B is an enlarged exploded view of the coupling assembly shown inFIG. 6A.

FIG. 7A is a cross-sectional view taken along line 7—7 in FIG. 4illustrating the actuators in an extended condition.

FIG. 7B is a cross-sectional view taken along line 7—7 in FIG. 4illustrating the actuators in a retracted condition.

FIG. 8 is an enlarged side elevational view of a portion of the endeffector illustrated in FIG. 2.

Before one embodiment of the invention is explained in detail, it is tobe understood that the invention is not limited in its application tothe details of construction and the arrangements of the components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Also, it is understood that thephraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including” and “comprising” and variations thereof herein is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items. The use of “consisting of” and variations thereofherein is meant to encompass only the items listed thereafter. The useof letters to identify elements of a method or process is simply foridentification and is not meant to indicate that the elements should beperformed in a particular order.

DETAILED DESCRIPTION

FIG. 1 illustrates a containerization and palletizing system 30. Theillustrated system 30 includes two cells 32, 34, each equipped with agantry or overhead-type robot 36. As one of ordinary skill in the artwill appreciate, the invention may alternatively be embodied in a systemhaving one cell and one robot, more than two cells and robots, or havingother types of robots.

Each cell 32, 34 has a frame 38 which may be secured to a hard surfacesuch as a concrete floor 40. The space between the frame members may beenclosed with a perimeter fence 42, a mesh, a similar material, or evenother types of walls. One or more gates or doors 44 may be provided topermit access to the interior of the cell. Each cell 32, 34 has aplurality of places or bays 46 for pallets 49, carts 50, and any othersuitable transport device (generically referred to herein as“containers”). Sensors (not shown) sense the presence or absence ofcontainers in the bays 46 and that information is communicated to asystem controller 55.

Mail trays, tubs, flats, and similar cartons (generically referred toherein as “trays”) 60 are brought into the cells 32, 34 by a conveyorsystem 66. The illustrated conveyor system 66 includes two generallyparallel conveyors. Sensors (not shown) positioned along the conveyorsdetect the location and presence of trays 60 on the conveyors.Information from the sensors is communicated to the system controller55.

The robot 36 in each cell 32, 34 is mounted on beams 76, 78 spanning thecell. The beams 76, 78 are mounted on powered and guiding tracks 80, 82,respectively. The robot 36 is movable along the beams 76, 78 and thebeams 76, 78 are movable on the tracks 80, 82. The tracks 80, 82 arepositioned generally parallel to the floor 40. Each robot 36 includes avertically telescoping arm 90, a turning disc or wrist 92, and an endeffector or gripper 95 (FIGS. 2-6).

FIGS. 2-5 illustrate the end effector 95, which is substantiallyidentical for both robots 36. The end effector 95 includes a pair ofcarriages 97 supported by a chassis 105. Each carriage 97 has a pair offingers 107 associated therewith. The fingers 107 include a journalportion 110 having a longitudinal axis 112 (FIG. 6A), and a bent orsupport portion 114 angled with respect to the longitudinal axis 112.Preferably, the bent portion 114 is angled about 80° with respect to thelongitudinal axis 112. The fingers 107 are shaped to accommodate a widevariety of trays 60. As will be described in more detail below, thefingers 107 are rotatable to an engaged position shown in solid lines inFIGS. 2-5, and to a disengaged position shown in phantom in FIGS. 2 and5. The bent portions 114 are disposed beneath a tray 60 when the fingers107 are in the engaged position, and are rotated clear of the tray 60when the fingers 107 are in the disengaged position.

With reference to FIGS. 2 and 5, in order to load containers havingshelves, the end effector 95 may also include a shelf-lowering assemblyincluding an actuator 115 slidable on a pair of rods 115 a, a finger 116a, and a shelf latch release mechanism 116 b. The actuator 115 isoriented with one rod 115 a above the other to create a high, narrowprofile. This orientation provides a more compact end effector 95, asthe actuator 115 does not consume a large amount of horizontal space.The actuator 115 selectively causes the finger 116 a and latch releasemechanism 116 b to extend into the container. The latch releasemechanism 116 b engages a latch that holds the shelf in an uprightcondition, and releases the latch so that the finger 116 a catches theshelf. The end effector is then lowered by the robot to lower the shelfto a horizontal position. The robot then continues to load trays intothe container.

Referring to FIGS. 3 and 4, one of the carriages 97 is a movablecarriage coupled to a track 117 by a plurality of slides or wheels 119and moved by a carriage actuator 121 (such as a rodless cylinder, butpreferably a multiple-pressure clamp cylinder) coupled to the chassis105. The clamp force of the carriage actuator 121 may be controlledusing a valve, such as an open/closed air control valve, and a proximityswitch, such as an intermediate-open proximity switch.

The end effector 95 also includes a mail measurement and containmentplate 160, which is used by the controller 55 to detect and measure theheight of trays 60 in containers. The measurement and containment plate160 includes two long arms 164 (FIG. 2) and a pair of cross members 166,although the plate 160 can have other shapes and provide similarfunctionality. The measurement and containment plate 160 is gravitydriven, supported by a pair of linear rods 170 which are mounted inbearings 176 (FIG. 3).

FIG. 6A illustrates one of the carriages 97; it being understood thatboth carriages 97 of each end effector 95 are substantially identicalunless specifically described otherwise. The carriage 97 includes a body208 and two actuators 210 which may be pneumatic, hydraulic, electric,or any other appropriate actuators. Each actuator 210 includes acylinder 214 with a first end 218 that is fixed to the carriage body 208with a suitable fastener or pin 222. Each actuator 210 also includes apiston 226 slidable with respect to the cylinder 214. A pin or othersuitable fastener 230 extends through the distal end of each piston 226.Alternatively, a clevis may be attached to or integrally formed with thepiston 226 and the pin 230 may extend through the clevis.

Each end of the carriage body 208 includes a cavity or space 234 inwhich a coupling assembly 238 is positioned. A pair of spaced-apartholes in each end of the carriage body 208 serves as journal bearings240 for the fingers 107. The journal portion 110 of one of the fingers107 extends through the coupling assembly 238 and the journal bearings240. The finger 107 is held in the journal bearings 240 above and belowthe coupling assembly 238. Because both ends of the carriage 97 aresubstantially identical to the other end, only one end is describedbelow.

With reference to FIGS. 6A and 6B, the coupling assembly 238 includes aclamp 242, an actuator arm 246, and a pair of spacers 250. As best seenin FIG. 6B, the clamp 242 is a split clamp including first and secondportions 258, 262, respectively. The first portion 258 includes a pairof holes through which the journal portion 110 of the finger 107extends. The second portion 262 includes a pair of clearance aperturesfor fasteners 266, and an aperture for a coupling pin 270. The fasteners266 extend through the clearance holes and thread into the first portion258 to hold the first and second portions 258, 262 together. Thecoupling pin 270 extends through the aperture in the second portion 262and into a hole in the journal portion 110 to couple the clamp 242 andfinger 107 together. The clamp 242 also includes cleats 274 for couplingthe clamp 242 and actuator arm 246 as described below.

The clamp 242 is preferably configured such that the finger 107 istightly sandwiched between the first and second portions 258, 262 sothat the coupling pin 270 is not exposed to all the shear stress causedby the weight of trays 60 being transported by the finger 107 and causedby rotation of the finger 107. The finger 107 may be removed andreplaced by removing the fasteners 266 and coupling pin 270, letting thefinger 107 drop through the assembly 238 under the influence of gravity,inserting a replacement finger 107 through the assembly 238, andreattaching the second portion 262 of the clamp 242, the fasteners 266,and the coupling pin 270.

The coupling pin 270 may be used to support the finger 107 and free upone hand of the installer when the replacement finger 107 is installed,making it easier to insert the fasteners 266. As an alternative to thecoupling assembly illustrated, and to further facilitate replacingfingers, the coupling pin 270 may be integrally formed with either thefirst or second portions 258, 262 of the clamp 242, and the fasteners266 may be replaced with an over-center clasp or another quick-releasefastener. The illustrated clamp 242 and coupling pin 270, and variationsthereof and alternatives thereto, provide a change-out or quick-releasemechanism that facilitates a relatively easy and quick changing ofdamaged or worn fingers 107.

Still referring to FIG. 6B, the actuator arm 246 includes a finger hole278 at one end, an actuator pin hole 282 at the opposite end, and aplurality of cleat holes 286. The journal portion 110 of the finger 107extends through the finger hole 278. The cleat holes 286 receive thecleats 274 of the clamp 242 to couple the actuator arm 246 and clamp242. The actuator pin hole 282 receives the pin 230 extending throughthe piston 226 of the actuator 210. If the end of the piston 226includes a clevis, the actuator arm 246 may extend into the clevis andbe pinned there. Thus, linear actuation of the piston 226 causes theactuator arm 246 to rotate about the longitudinal axis 112 of thejournal portion 110 of the finger 107, which causes the clamp 242 torotate due to the cleat 274 coupling, which in turn causes the finger107 to rotate due to the coupling pin 270 and sandwiching clamp portions258, 262.

FIG. 7A illustrates the actuators 210 in an extended condition, wherebythe fingers 107 are in the disengaged position (shown in phantom inFIGS. 2 and 5). FIG. 7B illustrates the actuators 210 in a retractedcondition, whereby the fingers 107 are in the engaged position. Thefingers 107 associated with each carriage 97 are counter-rotated by theactuators 210. As used herein with respect to the relative rotation ofthe pair of fingers 107 associated with each carriage 97,“counter-rotate” means that one finger 107 rotates clockwise and theother finger 107 rotates counterclockwise with respect to the fingersrespective longitudinal axes 112, as shown in FIGS. 7A and 7B.

Referring again to FIGS. 6A and 6B, the spacers 250 extend at leastpartially into the journal bearings 240 and abut the clamp 242 oractuator arm 246. The spacers 250 thereby space the clamp 242 andactuator arm 246 from the carriage body 208 to reduce friction. Thespacers 250 are preferably made of a low-friction, wear-resistantmaterial, such as high molecular density plastic. The spacers 250 mayalso include roller bearings to further facilitate the rotation of thefingers 107.

With reference to FIG. 8, fluid and electrical supply lines or hoses 290extend through the telescopic arm 90 to the end effector 95. The fluidsupply hose supplies the fluid used to actuate the various actuators115, 121, 210 on the end effector 95, and may, for example, providepressurized air or hydraulic fluid. The electrical supply line provideselectricity for the various sensors and electrically-powered componentsof the end effector 95. Other lines may also extend through thetelescoping arm 90, such as cables for relaying information from sensorsto the controller 55. The lines 290 are coiled on a support plate 294 toprevent or reduce tangling of the lines and pinching of the fluid hoseduring operation of the robot 36. Plugs 298 are provided in thetelescopic arm 90 and the end effector chassis 105 to easily disconnectand replace the lines 290. The plugs 298 facilitate servicing the robot36.

The operation of the system 30 will now be described in light of theabove disclosure. A tray 60, to be loaded into a container, is moved bythe conveyor system 66 beneath one of the robots 36. The controller 55moves the robot 36 over the tray 60 and the end effector 95 is loweredto position a pair of fingers 107 on either side of the tray 60 with thefingers 107 in the disengaged position. The fingers 107 are rotated tothe engaged position by actuation of the actuators 210 to the retractedcondition (FIG. 7B) and the movable carriage 97 is moved toward thefixed carriage 97 until the bent portions 114 of the fingers 107 arebeneath the tray 60. Then the end effector 95 is raised, lifting thetray 60 with the fingers 107. The downward force exerted on the top ofthe tray 60 by the containment plate 160 helps maintain the grip of thefingers 107. The robot 36 is moved over the container and the endeffector 95 lowered until the tray 60 rests on the container or onanother tray 60 in the container. The height of the stacked trays 60 ismeasured with sensors monitoring the movement of the linear rods 170 andis used by the controller 55 to determine when the container is fullyloaded. The actuators 210 are extended (FIG. 7A) to counter-rotate thefingers 107 to the disengaged position and the end effector 95 is raisedor otherwise moved clear of the tray 60 and container.

The present invention can be embodied in alternative systems. Forexample, each carriage 97 may support more than two fingers 107. Thefingers 107 may include substantially straight portions having bentportions disposed at 90° with respect to the straight portions. Bothcarriages 97 may be movable toward each other such that the carriages 97center the tray 60 with respect to the end effector 95. A singleactuator 210 may be used to counter-rotate two or more fingers 107through a linkage. Other possible combinations and alternativeconstructions of the features described herein would be readily apparentto those of ordinary skill in the art and are not discussed.

What is claimed is:
 1. A method of handling a tray, the methodcomprising: providing a robot having an end effector supporting firstand second carriages; providing a pair of fingers for each carriage;moving the end effector over the tray; grasping the tray with thefingers; moving the tray with the end effector to a container; anddepositing the tray in the container with the end effector bycounter-rotating the pairs of fingers.
 2. The method of claim 1, whereinsaid depositing step includes counter-rotating the fingers withactuators.
 3. The method of claim 1, wherein said depositing stepincludes counter-rotating each pair of fingers with a single actuatorthrough a linkage.
 4. A method of transporting an object using an endeffector having a first and second carriage, a first and second pair offingers, and at least one pair of actuators, said method comprising:positioning said end effector over said object; activating said pair ofactuators to rotate said first and second pair of fingers to an engagedposition; moving said first carriage toward said second carriage untilsaid first and second pair of fingers are beneath said object; elevatingsaid end effector to move said object to a desired location; andactivating said actuators to rotate said first and second pair offingers to a disengaged position.